It is known that herbicidal compounds in known herbicides such as sulfonylurea compounds, sulfonamide compounds, chloroacetanilide compounds, thiocarbamate compounds, pyrimidinyloxy(thio)benzoic acid compounds, tetrazolinone compounds, pyrazole compounds, cyclohexanedione compounds, phenoxycarboxylic acid compounds, oxazinone compounds, and difluoromethanesulfonylanilide compounds represented by the general formula:
wherein R1 is a hydrogen atom, an alkyl group, or an alkoxyalkyl group, or a salt thereof have high herbicidal effects at low doses on annual weeds such as Echinochloa crus-galli, Cyperus difformis, Monochoria vaginalis, and Ammannia multiflora, and perennial weeds, such as Eleocharis acicularis, Sagittaria pygmaea, and Sagittaria trifolia or, in particular, paddy weeds, and have broad herbicidal spectra (see Patent Document 1).
However, these herbicidal compounds may be sometimes phytotoxic to rice, and such phytotoxicity is more severe in a bad environment such as a high temperature environment, sandy soil, or a water-leaking paddy field, and in a shallowly planted seedling or a seedling immediately after transplantation or seeding. Further, these herbicidal compounds may be phytotoxic when applied in excessive amounts unwillingly or accidentally.
Accordingly, more selective herbicidal compounds, or safeners to make herbicidal compounds more selective are now under way of development. Examples of safeners practically used include fenclorim for pretilachlor as a chloroacetanilide compound, and chlorazol for fenoxaprop-ethyl as an allyloxy compound. There has also been proposed an attempt of using a benzoyloxime ether compound as a safener for a sulfonylurea compound (see Patent Document 2). However, these safeners are used only for a particular herbicidal compound, and cannot be widely used.
There has also been proposed an attempt of attaining both of a high herbicidal effect and safety on rice crops by use of a herbicidal compound represented by the above-given general formula in combination with another particular herbicidal compound such as pretilachlor or butachlor (see Patent Document 3). However, a technique of attaining both of a high herbicidal effect and safety on rice crops without using a plurality of herbicide compounds has not been established yet.
Patent Document 1: Japanese Patent Laid-open No. 2000-44546 (claims and elsewhere)
Patent Document 2: European Patent Application No. 122231 (claims and elsewhere)
Patent Document 3: Japanese Patent Laid-open No. 2000-281513 (claims and elsewhere)